Talk:Hertz/Archive 1

Archive 1

Audio frequency ranges

I noticed that frequency ranges were listed for visible light, but only a few select audio frequencies were listed. Might it be useful to note that the range from roughly 20Hz to roughly 16KHz covers the ability of the human ear to distinguish sounds? Or even note the higher ranges (or lower) used by other animals (dogs, whales, etc)?

-- T.Moore— Preceding unsigned comment added by 207.247.25.2 (talk) 21:45, 2 July 2004 (UTC)

Good suggestion; thanks! I'll see to it. --Wernher 22:35, 2 July 2004 (UTC)

Hz and human range of hearing

Can someone help me understand why dog whistles are considered 'silent' (as in beyond the range of human hearing) when most of them are (at about 5800 Hz) well within the range of audible sound (20Hz - 16kHz) for human hearing? Thx.— Preceding unsigned comment added by Sieghi (talk • contribs) 02:27, 23 September 2004 (UTC)

Because the maximum human ear performances are in the middle frequencies. A sound as treble as 6kHz has to be quite loud for you to clearly hear it.— Preceding unsigned comment added by Army1987 (talk • contribs) 13:44, 2 December 2004 (UTC)

Hz of food and liquids

Is it possible to measure the Hz of liquids, food stuffs, and is a lower or higher reading preferable in health terms? Some nutritional products claim to have a higher Hz and are therefore better - is this a scam? — Preceding unsigned comment added by 211.31.87.16 (talk) 04:22, 2 December 2005 (UTC)

The term Hertz as described in this article is just a definition of inverse time, e.g. the number of times something happens in a second. The term Hertz does get used in Essential Oils and other health supplements, on the basis that the brain (or entire body) has an operating electrical frequency, and that if that frequency becomes too low you die - if you have a high frequency, you are better off. In my opinion, these tend to be a bit hocus-pocus - there are loads of frequencies you can measure from the body and it's easy to make a spurious measurement. As for food 'adding' to that frequency, hmm... Here's a page which takes it all seriously though: http://www.webdeb.com/oils/frequency.htm Tomisaac 13:17, 25 May 2006 (UTC)

"Deeper explanation"

This section has been moved here so it can be beaten into understandable shape before being re-inserted:

Hertz (Hz) is a basic a measurement of sound between .001Hz - 20,000+Hz. The lower the hertz, the deeper the level of noise, the higher the hertz, the louder (high-pitched) level of noise. Hertz is also a measurement of high-low noise frequencies forming by the content of the electromagnetism the frequency contains. The amount of content it contains is measured by the abundance of geometric pulsations the frequency holds. Therefore, the higher the pulsations, the more tighter the sound waves are bonded together. The lower the pulsations, the less the waves are bonded. Tight bonds create loud, high-pitched frequencies which do not travel far. Weak bonds create low, sometimes even distorted frequencies that travel further because there would be more sound waves since they would not be bonded together as the tighter bonded waves.

The above is confusing. The "bonding of waves"...I'm just not sure what that's about. Urhixidur 16:24, 2 January 2006 (UTC)

Let me pick apart the errors in this... --ssd 03:57, 9 January 2006 (UTC)

• Sound still exists above 20khz, although human hearing is typicall between 40hz and 15khz, so neither of these numbers (0.001 - 20k) is really relevant.
• "high-low noise" ?? meaningless.
• Noise (as in sound) is not relevant to "electromagnetism"
• Frequencies don't hold "geometric pulsations"
• sound waves are not bonded. Mixed maybe, but not bonded.
• "loud" is a function of amplitude. "high" is a fuction of frequency. The two are independant.
• It is true (for both sound and electromagnetic radiation) that high frequencies are atenuated faster than lower frequencies.
• I am not aware of any special distortion that low frequencies might have, even over long distances.— Preceding unsigned comment added by Ssd (talk • contribs) 03:57, 9 January 2006 (UTC)

I think that whole passage is just a bunch of nonsense inserted as a prank. -- M.C.— Preceding unsigned comment added by 69.181.75.84 (talk) 14:02, 10 May 2006 (UTC)

Well, if it is a prank, I think it is not funny anymore: I reverted it three times this weekend, and left messages to the anons who put it, but I'm confident it will come back... CyrilB 08:20, 12 June 2006 (UTC)

How much?

How much MBs make 1 GHz?— Preceding unsigned comment added by Gamehead (talk • contribs) 05:17, 31 August 2006 (UTC)

Wrong section bub...— Preceding unsigned comment added by 65.12.47.71 (talk) 05:31, 4 September 2006 (UTC)

Equivalence to FLOPS

Are the two terms FLOPS and Hertz interconvertable? If so, what is the conversion ratio? Jack · talk 20:47, 12 February 2007 (UTC)

It's like an old piston water pump. Hz is the number of times per second it pulls up a load of water and dumps it. To know how many tons per minute, you must also know how many loads it takes to lift a ton of water. So, your question depends on how many cycles your flopper takes to move a flop, which is at least as variable as the bore of piston pumps. Jim.henderson 00:53, 21 March 2007 (UTC)

Terahertz

I think the 'terahertz' search shouldn't be redirected to this page because this term is more likely used to describe the band of frequency between microwave and infrared. It should be pointed to http://en.wikipedia.org/wiki/T-rays instead. I admit that terahertz is a short for terahertz radiation, but as i'm working in this field, we usually call it 'terahertz'.— Preceding unsigned comment added by 129.127.28.58 (talk) 08:27, 17 March 2007 (UTC)

I second this, and would like to add T-wave to the list that should go to T-rays instead of Hertz. I hear there's a wikipedia principle saying "be bold", so I'm going to make the changes seeing as the original links are 3 years old. Oooh, I see someone has already made the change for 'terahertz'. 99.225.158.180 (talk) 16:45, 10 March 2008 (UTC)

Pronunciation

"gigahertz ... can be pronounced /ˈgigaˌhɝts/, with a hard /g/ sound or /ˈʒɪgaˌhɝts/ or /ˈdʒɪgaˌhɝts/". Really? I've never heard any of these pronunciations in English. Whoever wrote this needs to brush up on their IPA.

• /a/ is the sound of French/Spanish/Italian "a". This phoneme does not exist in English. The symbol required is /ə/ (schwa).
• /ʒ/ is not a "soft g". That is /dʒ/. /ʒ/ is the sound of French "g" before "e" or "i", as in "Gironde".
• /ˈdʒɪgəˌhɝts/ (roughly, "JIG-a-hertz") is rarely used, if ever. That pronunciation might well be a possible variant according to dictionaries, but anyone selling or using computers who used it would just be laughed at.
• /ˌ/ is used for secondary stress. "Gigahertz" has primary stress only. The fact that the vowel in the final syllable is not reduced to /ɚ/ does not mean that there has a secondary stress there. — 217.46.147.13 (talk) 15:29, 1 April 2008 (UTC)

Definition?

Isnt the definition 'one _cycle_ per second' rather than just 'one per second' ?— Preceding unsigned comment added by 83.250.34.34 (talk) 21:51, 5 August 2005 (UTC)

No, it is just one per second. --mikeaitch 14:53, September 4, 2005 (UTC)

Hertz can measure any repeating event, it does not need to be a wave or cycle. --ssd 03:44, 6 January 2006 (UTC)

SI defines it as one per second, but still requires it to be periodic---i.e. cyclic. Radioactivity is not periodic, and is measured in becquerel, counts per second, not hertz. —Preceding unsigned comment added by Alma Teao Wilson (talk • contribs) 21:50, 16 October 2008 (UTC)

Hertz should be moved to hertz

The article's title "Hertz" should be moved to "hertz". The article's not about the man, it's about the unit, which is lowercase by default when spelled out in full. (The symbol Hz is capitalized because it came from a proper name, like the B in dB.) -- Another Stickler (talk) 09:29, 20 December 2008 (UTC)

The capitalized "Hertz" is correct usage in a title; see http://www.bipm.org/en/si/si_brochure/chapter5/5-2.html . Hqb (talk) 11:03, 20 December 2008 (UTC)

Thanks. The link says SI units can be capitalized in "capitalized material such as titles", but where is it written that encyclopedia entries are "titles"? Dictionary entries are not. Encyclopedias give more information about an entry than a dictionary, but an entry is still just an entry. -- Another Stickler (talk) 20:23, 20 December 2008 (UTC)

All Wikipedia titles start with an uppercase letter, unless the entry name is universally written uncapitalized even at the start of sentences. Hqb (talk) 20:50, 20 December 2008 (UTC)

Where's the wikipolicy? -- Another Stickler (talk) 00:28, 21 December 2008 (UTC)

Never mind. Hqb, I got your response in talk:decibel. Thanks. -- Another Stickler (talk) 02:27, 21 December 2008 (UTC)

Electricity

Why isn't electricity frequency added? —Preceding unsigned comment added by Railroader96 (talk • contribs) 03:10, 30 December 2008 (UTC)

Weird coincidence

Herz, as well as being the name of the guy the unit is named after, also happens, by sheer coincidence, to be the German word for "heart." The human heart beats approximately once per second. Linguofreak 03:50, 7 April 2006 (UTC)

Not quite... the guy is "Hertz". "Heart" is "Herz". I would hazard a guess that "Hertz" (the name) comes from "Herz". But yes, there is a nice coincidence here regarding the human heart rate. — 217.46.147.13 (talk) 15:44, 1 April 2008 (UTC)

Ummm... No-one actually uses hertz to measure heart rate. The well-nigh-universal unit of heart rate is the beat per minute. Alma Teao Wilson (talk) 22:12, 16 October 2008 (UTC)

I have only just noticed, in the last few minutes, this wierd connection between Hetz and Hertz, albeit with slightly different spelling. Only a few decades late. Isn't there a term for people with names that match their occupation, or something that they are renowned for? Tabletop (talk) 07:16, 5 April 2009 (UTC)

Introduction

The introduction begins with some complicated formulae, and totally put me off hertz when coming to read about it, haha. Why can't articles on this sort of thing be written for the common person, without all the nerdy crap (the intro shouldn't have that). —Preceding unsigned comment added by Finnian9 (talk • contribs) 15:15, 7 June 2008 (UTC)

I fixed up the introduction to better comply with Wikipedia guidelines. Folks, please suggest further improvements. Salientdowns (talk) 22:51, 21 July 2008 (UTC)

Simple Wikipedia   —un4v41l48l3 (talk) 08:09, 7 May 2009 (UTC)

Megahertz redirect

I've added a redirect which is intended to read "'Megahertz' redirects here. For the German NDH Metal band, see 'Megaherz'." However my attempt at understanding the code has been only partially successful. I'm deeming the current version good enough, hopefully someone will spare a moment later to do it right. 174.46.172.13 (talk) 10:12, 28 May 2009 (UTC)

It is sorted out now. :) Pooty the Echidna (talk) 19:16, 1 June 2009 (UTC)

Add samples of common frequencies?

I thought it might be a good idea to add a section for common/important frequencies, so articles can link to them. For example, I was reading about the ear (why? it's wikipedia for cryin out loud) and it said general audible range is 20 Hz to 20kHz, and I thought "I wonder what those sound like." Now, I have programs to generate the frequency but not everyone does. I can easily make samples for any kind of frequency. And I don't really think another whole page is necessary. Good idea or bad idea?

-- un4v41l48l3 (talk) 03:58, 16 April 2008 (UTC)

Sounds great. It would be nice to have some kind of logarithmic scale to give some idea of very low frequencies up to very very high ones. I guess it's important to restrict it to periodic events. e.g. Rotation of earth -> seismic waves -> very low frequency transmission -> audio -> ultrasonics -> electronics -> microwaves -> terahertz imaging -> infra-red -> visible light -> ultra-violet -> x-rays -> gamma rays -> ??? Maybe the SI table could get some representative examples of frequencies at each step?cojoco (talk) 12:40, 6 May 2009 (UTC)

I agree. I'm not well versed in this area. That's why I was reading this page in the first place. I'm an audio guy, so that's the only perspective I take on this normally. I can, however, make some sound files that are just a sine wave at certain frequencies. Which ones do we need? I suppose we'll need to figure out which cps / Hz are "important." List here specific (or general) frequencies that you know are significant. Such as A440, which already has a file. Darn beat me to it! :) Anyway, leave your frequencies here. —Preceding unsigned comment added by Un4v41l48l3 (talk • contribs) 08:19, 7 May 2009 (UTC)

I found one. Binaural beats could use tones at 1000 and 1500 and at 30 --un4v41l48l3 (talk) 05:02, 20 June 2009 (UTC)

Hertz are an absolute, unitless measure

Hertz - cycles per second. The thing is, seconds are cycles. That makes Hertz a cycles-per-cycle kind of measurement. The "cycles" divide out and the result is just a number. =) —Preceding unsigned comment added by 74.195.28.79 (talk) 21:43, 25 October 2008 (UTC)

No, I don't believe you. That would also make revolutions-per-minute (RPM) a unitless quantity, which is just silly. Time is not cycles, Time is a dimension. cojoco (talk) 12:34, 6 May 2009 (UTC)

No, hertz is a measure of cycles per second. No other unit is needed. Read a textbook. —Preceding unsigned comment added by Ratfatcat (talk • contribs) 00:55, 17 December 2009 (UTC)

Vandalism

I just fixed a statement that read "Hertz sounds like Burts beans. I love Burts!" This is obviously a sad attempt to vandalize and degrade the purpose of wikipedia. This is not a forum! This page should be peer reviewed often or could be subjected to wikipedia edit-restriction. —Preceding unsigned comment added by Ratfatcat (talk • contribs) 01:00, 17 December 2009 (UTC)

Too detailed

the explanations about the applications of this measurement unit are way too detailed. More information isn't necessarily better; it just makes this article look like some guy's ramblings about anything slightly related to Hertz. If people want to know how CPUs work, they can go read the article about that. The long-winded and irrelevant information is degrading to the standard of the article.Owen214 (talk) 12:34, 23 June 2010 (UTC)

Chip speed

Is there a THz chip actually being used in the world today? Also, is it mathmatically possible for a yotta hertz chip to be created?— Preceding unsigned comment added by 71.111.7.23 (talk) 00:01, 13 December 2005 (UTC)

Speed of chips are limited by the switching speed of the component semiconductors and the distance the signal travels in a given time. In a Thz, an electron could (very optimistically) travel 3nm, which is close to the size of the width of the traces in some chips. --ssd 03:44, 6 January 2006 (UTC)

I'd like to know which Home-based PC uses a 6GHz PPC. -- —Preceding unsigned comment added by 178.239.49.141 (talk) 17:48, 5 October 2010 (UTC)

Weak points and errors

• As for any derived unit in a coherent system, the presentation should start with the defining equation, in this case $f=1/T$ for a periodic (cyclic) phenomenon with period (cycle duration) $T$. This allows defining Hz (hertz) as the reciprocal of s (second). Letting $f=x{\text{ Hz}}=x/(1{\text{ s}})$ yields $x=(1{\text{ s}})/T$, showing that $x$ is the number of cycles per second. This is irrespective of the nature of a cycle. If a cycle consists in displacing a volume $V$ by one stroke of a piston pump, the flow $Q$ is given by $Q=Vf$. If a cycle consists in a full-circle angular rotation (physical or conceptual, as in AC), the angular frequency ${\text{ω}}$ is given by ${\text{ω}}={\text{τ}}f=2{\text{π}}f$.
• If one has defined $T{\text{ := }}2{\text{ s}}$, then it is incorrect to state that $T$ is the period in seconds. Indeed, $T$ is the period (period!) and 2 is that period in seconds. In fact, $T=(1/1800){\text{ h}}$. Similar observations hold for frequencies. This should be carefully observed everywhere (e.g., in the legend below the animation). Boute (talk) 14:20, 26 April 2011 (UTC)

"T is the frequency in seconds" and such expressions are unfortunately very common in wikipedia physics articles -- for one of many examples see Ampère's circuital law. I'm usually opposed to this and never do it myself, for the reason you said (it goes against the logic and algebra of units). But I made an exception for the caption because brevity is so important in a caption, and the equation T=1.0s was so simple that I didn't think anyone would get a wrong idea. More specifically, I wanted to say something like: "f is expressed here in Hertz and the abbreviation for Hertz is Hz, and T is expressed here in seconds and the abbreviation for seconds is s". But I couldn't think of any other way to do that without being too wordy. You're welcome to try! :-) --Steve (talk) 01:30, 27 April 2011 (UTC)

It is indeed regrettable that Wikipedia articles are generally quite sloppy (an unavoidable consequence of the editing policies), but setting examples by always trying to do things right may help a little. Here is a proposal for the caption, maintaining its original brevity.

"Three flashing lights, from lowest frequency (top) to highest frequency (bottom). f is the frequency and f = x Hz indicates that x is the number of flashes per second. T is the period and T = y s indicates that y is the number of seconds per flash. T and f are each other's reciprocal: f = 1/T and T = 1/f."

Variants: replacing y by 1/x, or mentioning that y = 1/x. Boute (talk) 09:25, 27 April 2011 (UTC)

I like it, but I fear it may still be confusing to people: For example, in "T = x s", the letter x is a variable while the letter s is the name of a unit--this is a confusing string to someone who doesn't know to expect that. Remember, some people will read this article before learning even grade-school algebra. Also, you forgot to say that Hz means Hertz and s means second. But it's close.... This is just my opinion. :-) --Steve (talk) 14:45, 27 April 2011 (UTC)

I took a shortcut in typesetting, assuming you would take care of that (in your figure and caption, T and f were not in italics either). Here is the "prettyprint" version, also making the reference to the lights more explicit.

"Three flashing lights, from a frequency $f=0.5{\text{ Hz}}$ (Hz = hertz) at the top to $f=2{\text{ Hz}}$ at the bottom. $f=x{\text{ Hz}}$ indicates that $x$ is the number of flashes per second. $T$ is the period and $T=y{\text{ s}}$ (s = second) indicates that $y$ is the number of seconds per flash. $T$ and $f$ are each other's reciprocal: $f=1/T$ and $T=1/f$." Boute (talk) 16:02, 27 April 2011 (UTC)

Sounds good! I'm happy for you to change it. (Sorry if I was being compulsive.) :-) --Steve (talk) 04:31, 28 April 2011 (UTC)

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Flashing figure

Is anyone else distracted by the animation on this page? --Kvng (talk) 15:47, 18 January 2011 (UTC)

I have WP:BOLDly replaced the figure. --Kvng (talk) 18:16, 24 May 2012 (UTC)

Although I was also distracted by the lights - I would have liked to see a "STOP" button, or better still a "START" button, the replacement picture does not convey anything to me. At least the lights illustrated what hertz was about. I feel that they should be reinstated - anyway, hertz do not have to be sinusoidal.Martinvl (talk) 18:34, 24 May 2012 (UTC)

I edited the animation in many ways to make it less annoying / distracting: [1]. I will try putting it back on the page soon...the thumbnails haven't been regenerated yet. --Steve (talk) 20:13, 31 May 2012 (UTC)

UPDATE: The (edited) image is now back on the page. Comments? --Steve (talk) 14:24, 1 June 2012 (UTC)

Why the discussion about Celsius?

-Celsius is not an SI unit, so the discussion about "degree Celsius" following the SI convention of being lowercase because the "d" in degree in lower case makes no sense to be included in this article. Putting it in the article about Celsius would be appropriate.

-Also, the explanation in the article is a somewhat misleading interpretation of http://www.bipm.org/en/si/si_brochure/chapter5/5-2.html, which makes the point that Celsius is capitalized because it is a proper name (no correlation with SI convention which does not capitalize proper names in units).

On that note, how exactly did that entire section happen? I couldn't find where it was located on the edit portion... help? ChunyangD (talk) 23:40, 13 April 2013 (UTC)

Never mind, I found out that it was just a template for SI lowercase conventions. I guess that it is unavoidable. ChunyangD (talk) 23:46, 13 April 2013 (UTC)

Relationship between angular and normal frequency

The formula ω=2πf expects that f is in Hz and ω is in rad/s. In other words, the quantities ω and f are unitless and normalized to 1 rad/s and 1 Hz, respectively.

I think it might be better to write the original formula as ω=2π(rad/s/Hz)f without dropping the units. If ω and f are treated as quantities with units, then ω=2π(rad/s/Hz)f and 2π rad/s=1 Hz, so 2π(rad/s/Hz)=1 and ω=f.

Using the latter approach, it is unnecessary to say that f has to be in Hz and ω has to be in rad/s. For example, ω could be in deg/s, then ω=2π(rad/s/Hz)f=360(deg/s/Hz)f. Or, ω could be in rev/s, then ω=1(rev/s/Hz)f, or simply ω=f.

Of course, I'm assuming that 1 revolution of phase = 1 cycle and 1 Hz = 1 cycle/s = 1 revolution/s. Maybe this isn't the correct interpretation of Hz (which I'm still confused about). Certainly the old cycle/s unit implied a cycle (or revolution) of phase angle per second.

We can also look at a formula for converting feet to meters. Let x and y both have a dimension of length, then

x = 0.3048 (meters/ft) y.

It's unnecessary to specify the units of x and y. Writing the equation this way makes it easy to see what happens if y has units of ft and x has units of meters, but the formula could easily be rewritten to use km and miles, for example. The underlying truth is that x=y: they are the same physical length. We are just converting between standards of measure of a particular dimension. The same could be said for ω=2π(rad/s/Hz)f or ω=f. — Preceding unsigned comment added by Mk29 (talk • contribs) 16:04, 14 August 2013 (UTC)

The statement "In other words, the quantities ω and f are unitless" is incorrect. In this case both ω and f have dimensions and these dimensions are not necessarily Hz and rad/s. The variable ω could be rad/min and f would be in rpm and the relationship would still hold (as long as you used minutes rather than second as your base unit for time). The variables ω and f represent two different quantities - angular frequency and rotational frequency. Martinvl (talk) 16:12, 14 August 2013 (UTC)

I disagree. There are two ways to write a formula. The first is to just have the output units be set by the input units. The other way is to specify the units of all of the inputs and outputs of the formula. The formal way to evaluate this formula is to normalize all of the inputs to the formula by their expected unit. If a formula expects a magnetic flux density in Tesla, then we take our magnetic flux density, divide by 1 Tesla, and insert it. Then our original magnetic flux density could be in any unit we so choose. The division by 1 Tesla scales the unit appropriately and results in a unitless number to insert into the formula. Similarly, we take our unitless output, multiply by the expected output unit, and get the result. Mk29 (talk) 16:21, 14 August 2013 (UTC)

Regardless, could you comment on the rest of the content? I think what you disagree about is a minor issue in the overall point of my post. Do you think that ω=2π(rad/s/Hz)f is incorrect? Mk29 (talk) 16:26, 14 August 2013 (UTC)

Yes I do. Firstly it is totally unorthodox to include the units of measure in the way that you have done, secondly is is totally unorthodox to incorporate two quotient signs in a single entity as you have done ("rad/s/Hz") and thirdly there are a multitude of units that can be used - including radians per minute and revolutions per minute. Martinvl (talk) 14:33, 15 August 2013 (UTC)

Would you be happy if I wrote the equation as ω/(rad/s)=2π f/(Hz)? Note that this is the same equation. This style is accepted by many institutions, in particular, you can see the 2005 IEEE Standards Style Guide p.29. This is known as a quantity equation, an equation which is correct regardless of the units used. And, I don't know why you need to nit-pick the two quotient signs. It is unambiguously interpreted as (rad/s)/Hz if you follow the standard order of operations. I agree that the equation holds so long as you are converting cycle/time to rad/time, as long as the time units are consistent. However, the equation doesn't work in general for any appropriately dimensioned units. For example, you can't get ω in deg/s for f in turns/hr, like you could with my proposed equation.--Mk29 (talk) 14:57, 15 August 2013 (UTC)

See also http://physics.nist.gov/cuu/Units/units.html and Gupta. Units of Measure..--Mk29 (talk) 14:57, 15 August 2013 (UTC)

I could not find an equation of the form ω/(rad/s)=2π f/(Hz) in the IEEE Standards Style Guide. I found a number of equations of the form ω=2πf though on pages 28-20. Would you please give me the page number where you found an equation of the form that you propose. Martinvl (talk) 15:36, 15 August 2013 (UTC)

See the top of page 30. There is an equation for converting between Kelvin and Celsius. It is written as t/°C=T/K-273.15, just as I am writing ω/(rad/s)=2πf/Hz. The point is that the style of writing a variable divided by a unit is acceptable and unambiguous. In the first example, I plug in the quantity T with units K, the K cancel, I subtract the unitless number 273.15, and I get a unitless answer. Now, I multiply this unitless answer by the unit °C to recover t, the quantity with units °C. Similarly, I plug in the quantity f with units Hz, the Hz cancel, I multiply by 2π, and I get a unitless answer. I multiply this unitless answer by rad/s to recover the quantity ω with units rad/s. I mentioned "quantity equations" earlier. Quantities are described by ISO 31.--Mk29 (talk) 16:18, 15 August 2013 (UTC)