Who can tell me something about physics? You can also copy, the more the better.

1. Light travels fastest in a vacuum. Light is not the slowest (because static is relative, but the speed of light in vacuum is absolute), only slower-the place with the slowest speed of light is not in the place with high density (if the medium is opaque, photons will be absorbed by half, so where can we get the speed? However, the current science can reduce the speed of light to near standstill (moving tens of nanometers a second, and one nanometer equals one billionth of a meter): a kind of "super optical trap" is made of silicate crystals doped with rare earth element Pr, so that light energy can be "frozen" in this trap for one second.

2. As for sound, because it propagates through the medium, the more stable, regular and arranged the molecular structure of the medium, the easier it is for sound to propagate. So the speed of sound in solid is the fastest, followed by liquid, and the speed of sound in gas is the slowest.

Light is an electromagnetic wave, but light and electricity are two different things. Light is composed of photons, which are a form of energy. Electricity is made up of electrons, which are real particles. Electrons are one of the basic particles that make up atoms, and they have a certain volume, and their particle nature is the main one. Photons are particles that transfer interaction for electrons, that is, the interaction between electrons (mutual energy transfer) depends on photons. Photon has no certain volume and is a quantitative form of energy (a photon can be understood as the smallest unit of light energy). When electrons jump at different energy levels, they can radiate electromagnetic waves, and the visible part can be felt by people (the wave-particle duality theory of light can be regarded as the composition of photons), but it cannot be said that photons are electrons. Light and electricity are easily confused because matter emits light at the same time. Because the mass of electrons is very small, it can be increased with very little energy, and particle accelerators can increase the speed of electrons to very, very close to the speed of light; The lower the temperature, the lower the activity of atoms, and the particles in atoms are no exception. When the temperature reaches absolute zero (-273. 15℃), all particles will "freeze", but this is impossible because absolute zero cannot be achieved. At present, the low temperature that humans can achieve is only 0.5 Kelvin (that is, 1% Celsius) higher than absolute zero. At this time, the speed of electrons should also be the slowest.

Light-year is only the longest astronomical length unit, but it is not the longest length unit. Much longer, such as parsec (1 parsec =3.26 16 light years, one light year equals the length of light in a vacuum), one million parsec (not to mention), and the distance between galaxy clusters is about 25 million parsec. In ancient China, there were some deeper units of length. As far as integers are concerned, they are 1, 10, 100, 10000, 10000, 10000, respectively. Ten thousand is the fourth power of ten (plus four zeros), and the largest infinite number is equal to one times ten to the sixty-eighth power.

5. Egypt is only the smallest astronomical length unit, and there are smaller ones, such as picometers, femtometers and Amis (one Ami equals one hundredth of a micron). In ancient China, the units with scores below are: minute, centimeter, milli, silk, sudden, micro, fiber, sand, dust, Egyptian, misty, fuzzy, erratic and bearded.

6. "The most natural science" is that there are thousands of articles on Baidu, and it is impossible to list them one by one. In addition to what is said upstairs, you can also refer to/let/04zcb/neirong/14sb/k0030.htm.