203
votes
If I stood next to a piece of metal heated to a million degrees, but in a perfect vacuum, would I feel hot?
I'm more so asking about thermal radiation emitted by it.
Here's a quantitative estimate.
Suppose that the hot plate remained intact long enough to do the experiment. For a rough estimate, we can ...
- 53.6k
180
votes
Would a pin head heated to 15 million degrees Celsius kill everyone in a 1000 mile radius?
In this occasion Vsauce rather dropped the ball, I should think. As the other answers show, the claim as stated doesn't make much sense when you put in the numbers, and if you chase the source to its ...
- 131k
167
votes
Accepted
Why do spaceships heat up when entering earth but not when exiting?
Aerodynamic heating depends on how dense the atmosphere is and how fast you are moving through it; dense air and high speed mean more heating. When the rocket is launched, it starts from zero velocity ...
- 90.1k
159
votes
Accepted
Why doesn't water boil in the oven?
The "roiling boil" is a mechanism for moving heat from the bottom of the pot to the top. You see it on the stovetop because most of the heat generally enters the liquid from a superheated ...
rob♦
- 86.3k
149
votes
Why don't miners get boiled to death at $4$ km deep?
As noted in CountTo10's answer, the main answer is simple - miners don't "boil" because the mines use suitable cooling and ventilation equipment, plain and simple.
That said, there is a contradiction,...
- 131k
126
votes
Accepted
Why does water stop boiling immediately after turning off the heat?
In large part because under normal circumstances water doesn't get hotter than boiling - at that point it becomes steam, as you know. You can add heat and boil it away faster, but the water can only ...
- 1,016
121
votes
Could a candle theoretically melt iron?
No. The candle can only transfer heat into the iron as long as the candle is hotter than the iron. The temperature of a flame depends heavily on the chemicals being burned. A typical candle burns at ...
- 2,634
116
votes
Accepted
Why doesn't increasing the temperature of something like wood or paper set them on fire?
Before answering your question, it is important to understand how ignition of a solid material occurs. For fuels that contain hydrogen and carbon like paper, Ignition is a gas phase phenomenon . It is ...
- 69k
115
votes
Accepted
What would happen if a 10-kg cube of iron, at a temperature close to 0 kelvin, suddenly appeared in your living room?
Nothing overly dramatic, though it would be cool to look at. The cube would very quickly become covered by a layer of nitrogen/oxygen ice as the air which came into contact with it froze. Further ...
- 67.5k
106
votes
Accepted
Why don't you get burned by the wood benches in a sauna?
First of all, I hope you sit on a towel. But even when you touch wood with your bare skin, you don't get burned. This indeed has to do with thermal conductance.
The point is not the heat transfer ...
- 10.3k
101
votes
Accepted
Is the Boltzmann constant really that important?
We can understand all of this business if we visit the statistical mechanics notion of temperature, and then connect it to experimental realities.
Temperature is a Lagrange multiplier (and should ...
- 24.2k
93
votes
Accepted
Why does a room not warm up faster when I put the heater's thermostat on a higher value?
Because you're only changing the temperature at which the heater is supposed to stop working.
It is always working at the same power, regardless the temperature difference. But for higher temperature ...
- 1,304
91
votes
If I stood next to a piece of metal heated to a million degrees, but in a perfect vacuum, would I feel hot?
The other answers provide good explanation why your friend is wrong in this case. I just want to point how you could both easily reach the same conclusion without knowing much of the physics involved:
...
- 3,018
79
votes
Accepted
Could I survive at (or near) absolute zero with a very, very, very thick sweater?
A super-thick sweater probably isn't the way to go - you may be better off wrapping yourself in aluminum foil.
The body loses heat through a handful of mechanisms:
During conduction, your body ...
- 67.5k
76
votes
Accepted
Does anything in an incandescent bulb actually reach its color temperature (say 2700 K)?
Does any component in an incandescent lightbulb actually reach temperatures in the thousands of degrees?
Yes, the filament. This is why the filaments are made of tungsten, which has a melting point ...
- 1,943
70
votes
Why can't the Earth's core melt the whole planet?
Think about a frozen-over lake in the winter. The water underneath is liquid, but it doesn't melt the ice. In fact, it wasn't even able to stop the ice from freezing as the weather got colder in the ...
- 3,085
69
votes
Why does water stop boiling immediately after turning off the heat?
Because the water — and therefore the steel — is not hotter than 100 °C
Assuming normal pressure (1 atmosphere), water boils at 100 °C. The water cannot become hotter than that because then it turns ...
- 1,110
67
votes
Bush fires and heat waves, the real mechanics?
This is more a question of chemistry and biology than physics.
Solid objects don't burn (try dropping a lit match on a piece of structural lumber sometime -- it'll just go out). Instead, they ...
- 1,713
67
votes
Why does pressure in a thermos increase after shaking up hot water and soap?
When you pour the hot water in, the air inside the thermos is still quite cold (ambient temperature, approx.)
But then when you shake it up the cold air is heated by the hot liquid. Gases expand ...
- 35.1k
65
votes
Why do spaceships heat up when entering earth but not when exiting?
Recently I read up on spacecrafts entering earth using a heat shield. However, when exiting the earth atmosphere, it does not heat up, so it does not need a heat shield. Why is this so?
A spacecraft ...
- 1,702
65
votes
Accepted
Why does moving air feel colder?
If the air was still, body heat warms a thin layer of air next to the skin. This warm air would stay near the skin, separating it from the cold air. Wind, however, continuously blows away this warm ...
- 24k
63
votes
What makes cheese so effective at absorbing microwaves?
It is because cheese has a nice combination of water and fat. The water is important since the microwave transfers energy to it by making the water molecules vibrate. On the other hand, oils, in ...
- 17.6k
63
votes
If temperature is amount of kinetic energy of particles, then how can there be a cold breeze?
The average speed of an air molecule can be approximated by the following equation, which is exact only in the case of an ideal gas:
$$\langle v \rangle = \sqrt{\frac{2RT}{M}}$$
This means at $25$°C ...
- 16.1k
62
votes
Accepted
Does the halflife time of a radioactive material decrease if its temperature increases?
In the years following the discovery of radioactivity, physicists and chemists (recall that Rutherford was given the Nobel prize for Chemistry!) investigated the effect of heating radioactive ...
- 34.9k
62
votes
Accepted
Why is the air inside an igloo warmer than its outside?
An igloo is not made from ice, but made from compressed snow. Snow is basically semi-frozen water or frozen crystalline water.
Contrary to intuition, snow has actually got very good insulating ...
- 29k
58
votes
Why do we "feel" steam at 100 °C as hotter than water at 100 °C?
TL;DR: You have probably not been exposed to 100°C water in either phase and even if you had, you could not have reasonably felt its temperature on account of receiving a third-degree burn. Hot water ...
- 5,980
56
votes
Accepted
Sun's power density compared to a compost heap
Your (gardener's) intuition is wrong. If you increase the size of your compost heap to the size of a star, then its core would be as hot as that of the Sun. All other things being equal (though ...
- 128k
56
votes
When snow falls, temperature rises. Is this due to entropy?
Yes. A simpler way to look at this is that because freezing, as well as resublimation (turning a gas directly into a solid) emits heat. It may seem strange but consider this: you need to put in heat ...
- 3,637
55
votes
Accepted
Could a candle theoretically melt iron?
I'll try a simple explanation. Assume that there are no phase transitions initially. As you heat a body, its temperature rises, and it radiates energy into the surrounding space according to $$P = A\...
- 3,616
Only top scored, non community-wiki answers of a minimum length are eligible