Wikipedia:Reference desk/Archives/Science/2018 June 28
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June 28
[edit]Reporter gene affecting expression of other genes?
[edit]Are there any cases where a reporter gene in an experiment has affected the expression of other genes which were being studied? --129.215.47.59 (talk) 13:21, 28 June 2018 (UTC)
- It says right in the article that you have to be careful with your placement lest the reporter affect the expression of the target too much. So in all experiments the reporter gene has affected the expression of other genes which were being studied. Abductive (reasoning) 05:55, 3 July 2018 (UTC)
Wristwatch + thermometer = useless?
[edit]Are thermometers useless in wristwatches? Wouldn't our temperature contribute significantly to any temperature it shows? Specially if you are wearing it under a sleeve, I don't see how it can avoid this effect.Doroletho (talk) 17:40, 28 June 2018 (UTC)
- Say someone wakes up one day. Wow this is a cold June, I shouldn't have left the window open. I want to know how cold it is. I don't own any other thermometers. So he looks at the wristwatch. Sagittarian Milky Way (talk) 18:05, 28 June 2018 (UTC)
- The solution, of course, is not to rely on the thermometer while it is in contact with your wrist. Attach it to a backpack, wrap it around outside your coat sleeve, or otherwise insulate it from your body. TenOfAllTrades(talk) 18:52, 28 June 2018 (UTC)
- So, kind of a useless feature, in a device designed to be in contact with the wrist. --Doroletho (talk) 19:20, 28 June 2018 (UTC)
- (e/c) It probably has an error correction algorithm to compensate (but I wouldn't expect much accuracy). It is possible (in theory, at least) that if it is a smart-watch that it gets temperature based on geolocation -- I have a "smart" thermometer that gets indoor temp & humidity from sensors, and outdoor readings as if by magic (presumably via geolocation). —107.15.157.44 (talk) 19:24, 28 June 2018 (UTC)
- I've had a watch with such a feature, and yes, it's entirely useless while worn. According to the manufacturer "If you are wearing your Suunto Core on your wrist, you will need to take it off in order to get an accurate temperature reading because your body temperature will affect the initial reading." [1] Most sensors and many microprocessors have a temperature sensor built-in, so typically manufacturers can display this information for "free", albeit highly inaccurate in this context. Cars try mitigating this by placing the sensor on the bottom of the front grill, although this picks up heat from the road, so it's also not entirely accurate. A watch is too small a device to realistically decouple it thermally from the body, but yes, quite handy if you looking for your skin temp. Drewmutt (^ᴥ^) talk 19:46, 28 June 2018 (UTC)
- Is this watch waterproof? If it is, then, maybe it can be accurate when swimming. In this context, I'd say that it might be a useful feature for those who spend long time in the water like scuba divers, open water swimmers, long-distance swimmers and so on.Hofhof (talk) 23:32, 28 June 2018 (UTC)
- Casio says essentially the same thing: "Temperature measurements are affected by your body temperature (while you are wearing the watch), direct sunlight, and moisture. To achieve a more accurate temperature measurement, remove the watch from your wrist, place it in a well ventilated location of of direct sunlight, and wipe all moisture from the case."[2] The moisture, of course, can cause evaporate cooling. --Guy Macon (talk) 21:38, 29 June 2018 (UTC)
- I suppose one could always carry a Stevenson screen around with one, and put the watch in it whenever one wanted to know the temperature. DuncanHill (talk) 21:45, 29 June 2018 (UTC)
Big Bang question
[edit]Reading the Wikipedia article on Big Bang I ran into this quote at "Inflation and Baryogenesus" section:
"After inflation stopped, reheating occurred until the universe obtained the temperatures required for the production of a quark–gluon plasma as well as all other elementary particles."
Reheating must have required tremendous energy. Where did this energy come from?
Thanks. AboutFace 22 (talk) 22:46, 28 June 2018 (UTC)
- It comes from the energy stored in the inflaton field see here for details. Count Iblis (talk) 22:56, 28 June 2018 (UTC)
- A little more detail: Inflation (cosmology)#Reheating. --47.146.63.87 (talk) 06:35, 30 June 2018 (UTC)
Big Bang question II
[edit]How can we know that all matter was indeed compressed in an area the size of an apple? Couldn't it be that all matter just sneaked into our universe from a parallel universe thru a tiny hole. --Hofhof (talk) 23:37, 28 June 2018 (UTC)
- Has a parallel universe ever been observed? ←Baseball Bugs What's up, Doc? carrots→ 01:16, 29 June 2018 (UTC)
- Has our universe ever been observed being compressed to the size of an apple? Honestly, if a mathematical model can discard this possibility, it could also open the door to the possibility of parallel universes. --Hofhof (talk) 02:24, 29 June 2018 (UTC)
- Obviously not. But the Big Bang is a scientific theory which does what scientific theories do: explain past observations, and predict future observations. Have there been any observations that suggest there could be a parallel universe? And there's the obvious dilemma: Where did that universe come from? ←Baseball Bugs What's up, Doc? carrots→ 09:54, 29 June 2018 (UTC)
- They could have been necessary (parallel or sequencial) for a universe to have the necessary elements and proportions to make life possible, but have never been observed, of course. I unfortunately don't have the formulas to evaluate the size of the universe at that point without doing more research myself, but I doubt that it was invented arbitrarily... Also, it was likely that size only at a precise moment in time (and a very short moment). —PaleoNeonate – 03:51, 29 June 2018 (UTC)
- Has our universe ever been observed being compressed to the size of an apple? Honestly, if a mathematical model can discard this possibility, it could also open the door to the possibility of parallel universes. --Hofhof (talk) 02:24, 29 June 2018 (UTC)
- There's no evidence the universe was not infinite in size. It is the space in the universe that expands. Dmcq (talk) 13:36, 29 June 2018 (UTC)
- One puzzlement: If you could magically transport back to the beginning of the universe, by what mechanism would you determine if it was the size of an apple or any other specific object? ←Baseball Bugs What's up, Doc? carrots→ 13:56, 29 June 2018 (UTC)
- I am not sure if the OP is facetious or not. Anyway we are currently observing that the universe is expanding. We infer that it was smaller in the past. We also have observed singularities, so we know they are definitely possible. Modelling this easily leads us back to a very small universe. That does not explain absolutely everything, but it is more reasonable than magical invisible pink unicorns just wishing the universe to exist, or parallel universes with holes between them, transferring matter and energy that has the mass of an other universe, since we have no observation of that phenomenon, nor any model that leads to that. --Lgriot (talk) 14:49, 29 June 2018 (UTC)
- Have we observed singularities?? Bubba73 You talkin' to me? 02:00, 1 July 2018 (UTC)
- Yep, we have observed the gravitational effects of many black holes on other objects like stars, and their gravitational effects on light (lensing), and the energetic emissions of the matter that is falling into them. We have also observed the rippling of space-time of merging black holes. That is enough observations as far as I am concerned. --Lgriot (talk) 14:32, 2 July 2018 (UTC)
- Small gripe: we have observed the effects of objects consistent with GR black holes, but we most definitely have not observed gravitational singularities. Even in standard GR the singularity is usually hidden behind an event horizon. There have been computations that predict the emergence of naked singularities, but those have not been observed experimentally. The consensus is that GR breaks down before physical singularities form, and AFAIK the jury's out on whether a proper theory of quantum gravity has true singularities. --Link (t•c•m) 17:46, 2 July 2018 (UTC)
- By that logic I claim that you have never "observed" your left hand. All you have done is capture some photon using your retina, some of which might have bounced off your hand, but you have never actually seen your hand, just some photons, so maybe you don't have a hand and the photons were emited by some clever device which made their pattern consistent with having a hand. --Lgriot (talk) 12:24, 5 July 2018 (UTC)
- Small gripe: we have observed the effects of objects consistent with GR black holes, but we most definitely have not observed gravitational singularities. Even in standard GR the singularity is usually hidden behind an event horizon. There have been computations that predict the emergence of naked singularities, but those have not been observed experimentally. The consensus is that GR breaks down before physical singularities form, and AFAIK the jury's out on whether a proper theory of quantum gravity has true singularities. --Link (t•c•m) 17:46, 2 July 2018 (UTC)
- Yep, we have observed the gravitational effects of many black holes on other objects like stars, and their gravitational effects on light (lensing), and the energetic emissions of the matter that is falling into them. We have also observed the rippling of space-time of merging black holes. That is enough observations as far as I am concerned. --Lgriot (talk) 14:32, 2 July 2018 (UTC)
- Have we observed singularities?? Bubba73 You talkin' to me? 02:00, 1 July 2018 (UTC)
- I may be wrong, but as I understand it, at least some current models of the big bang do not require a small universe, just a dense universe. In other words, the universe might have been infinite at the time of the big bang - it just suddenly expanded a lot. --Stephan Schulz (talk) 21:13, 29 June 2018 (UTC)
Collapsing asides about the nature of infinity. All this has wandered far too much into offtopic territory for this thread. If someone has questions (as opposed to opinions they want to vent), they are welcome to open a new thread (possibly at WP:RD/M) instead of hijacking someone else's thread. TigraanClick here to contact me 08:00, 4 July 2018 (UTC)
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To give a very short answer to a very short question, regardless of the tangents everyone went off on, the expansion of the universe, and the rate at which it is expanding can be expressed mathematically. If you run those numbers in reverse, you arrive at a point when it was all condensed into a single spot. Of course that's a very simplified answer, but I think it's what you were asking.