# Tag Info

56

Hiroshima exploded 67 terajoules of energy i.e. $6.7\times 10^{13}$ joules. We may calculate the mass of the Russian meteor assuming that the speed is $v=20,000$ m/s: $$\frac{1}{2} mv^2 = 6.7 \times 10^{13}$$ We obtain 335 tons. The numbers aren't precise but they're in the ballpark and reasonable. The Russian academy of sciences actually estimates 10,000 ...

13

John's answer is a good one, I just wanted to add some equations and addition thought. Let me start here: Heating is really only significant when you get a shock wave i.e. above the speed of sound. The question asks specifically about a $200^{\circ} C$ increase in temperature in the atmosphere. This qualifies as "significant" heating, and the ...

12

At the risk of being snarky (each definition is from wikipedia)... Comet - A comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma (a thin, fuzzy, temporary atmosphere) and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet. ...

10

The Perseids in August are always good with 30+ meteors per hour. If you can get to a dark sky, you won't be disappointed. The Leonids hit their thirty-three year peak just a couple years ago so it will be a while before they peak again. The Perseids peaked in the mid-1990s (I saw 200 meteors in 1.5 hours through a hole in the clouds that just showed Perseus,...

10

Remember that meteoroids are celestial objects. At these scales, it is quite common for relative velocities to be extremely large. When such a fast-moving object enters the atmosphere of the Earth, the air slows it down due to its viscosity. However, the meteor is moving very, very fast. Unlike most falling objects, it doesn't get a chance to even reach ...

9

Meteoroids come in a very large range of sizes, from specks of dust to many-kilometer-wide boulders. Explosions like that of the Chelyabinsk meteor are only found meteors that are larger than a few meters in size but smaller than a kilometer. Though the details are argued endlessly by those who study such phenomena (it is very hard to get good data when you ...

7

I suspect this is a formidably difficult question to answer from first principles. The cooling depends on the details of the air flow around your cylinder, and also on the temperature difference. An aeroplane flies at an altitude where the temperature is -50C, so the cooling is obviously going to be very different to say a baseball travelling at sea level. ...

7

The Moon has no atmosphere, so meteors would not heat up and glow as they descended, as they do on Earth. Comets, however, reflect light from the Sun, and thus can be seen from any sufficiently dark location.

7

Airburst, I think, it is called. An article on wired.com covers exactly this question the rock was already going very fast when it entered the Earth’s atmosphere. There is no way the air could get it down to terminal velocity – there just wasn’t enough distance for a rock this large. But this air resistance is essentially the reason that it ...

6

The duration of the energy release has a huge effect on the destructive potential. A single stick of TNT has roughly 1 MJoule of energy which is released in a fraction of a second. [1] Spread the same 1 MJ over an hour and you get 277 W or roughly the same power consumption as an ATI Radeon HD 7970. [2] Sources: [1] http://en.wikipedia.org/wiki/Dynamite [...

6

There are a few meteor showers that merit mentioning: Quadrantids: January 3, ZHR: 120 Eta Aquariids: May 6, ZHR: 60 Arietids: June 7, ZHR: 54 Perseids: August 12, ZHR: 90 Orionids: October 21, ZHR: 20 Geminids: December 14, ZHR: 120 Of course, these rate estimates are not absolute, and in rare cases some showers (for example, Leonids) can flare up, ...

5

This somewhat depends on your definition. It is reasonably likely that a huge impact on Earth could knock rocks into a loose orbit around us, or at least around the sun but coming close to us. It seems likely that some of these would eventually fall back to the Earth, being Earth-origin meteorites. The second possibility, that they landed on another world ...

5

The heat of atmospheric reentry and the sudden impact of, um, impact, certainly metamorphosize the minerals in a meteorite. That's a whole fascinating branch of geology. Before the metamorphosis, though, I don't think either of the other terms fit, unless you're talking about a meteor that has already been processed through a large body as lava and ejected ...

5

It's been a while since I set out specifically to watch a meteor shower but back when I used to do so I would typically watch in a prone position. Either lying on a blanket or slightly inclined on a folding lounge chair (and sometimes lying on a picnic table. The main reason, at least for me, is that you want to try to see as much of the visible sky as ...

5

The flash seen in this video may not be the glow of initial entry since the camera angle is angled somewhat along the path of the meteor; it is likely the active burning after the meteor has already entered the atmosphere. The mesosphere begins about 50 km above the earth's surface. However, the speed of sound in this region is a bit lower than the speed ...

5

Two terminology issues first. First, cosmology is the study of how the universe began and what will ultimately happen to it. Pieces of rock in our solar system have nothing to do with cosmology. Second, a meteoroid is a small solid body in the solar system. A meteor is what we call such a body while it is falling through our atmosphere, usually glowing hot ...

5

As of right now we have no way of deflecting an asteroid on its way to hitting the Earth. However there are lots of organisations tasked with looking into the issue. The Wikipedia article on Asteroid impact avoidance would be a good place to start. Also see the NASA Near Earth Orbit site for lots more background. You are quite correct than the kinetic ...

3

As a high velocity meteoroid encounters denser atmosphere, there exists an increasing pressure difference between its frontal and rearward areas. This plus the very high temperatures create the instabilities that ultimately cause the sudden destruction of the body. Chrondite meteoroids are more vulnerable to this type of destruction than iron/nickel bodies ...

3

Another issue with the object getting heated up, apart from the concerns already raised by AlanSE, is that even if you can put the air at the front of the object at 500 K, that doesn't bring the object heat to 500 K, not even after a long time, and certainly over its whole volume ! The main issues the size of the object and the fact that there will heat ...

3

When this meteorite entered the atmosphere, it was traveling at approx 36000 miles per hour. Now consider this fact; I have a roof rack that creates a howling sound when I speed up to 100 kph. This howling sound is caused by air moving past the roof rack. I can hear this howling sound with my car windows closed. If there were sensors mounted on the vehicle ...

3

All speed is relative. But an object that starts from rest at infinity will reach a velocity of about 11 km/s when it hits Earth, if Earth is the only thing pulling on it. At the same time, Earth is moving with an orbital speed of about 30 km/s. Their relative importance will depend on the direction from which the meteor is approaching - but on the whole ...

3

Meteors are essentially bits of rock that are independently in orbit around the Sun and which cross the Earth's orbit. If the Earth happens to be there at the same time then it will enter the Earth's atmosphere and we will see a meteor. The velocity of meteors is related to how fast they we going in their orbit around the Sun, combined with how fast the ...

2

At 4:30, light from the burning meteor reached the video camera. At that time the meteor was still in the air and it did not generate the boom. After 150 seconds the sound waves reached the video which means that the point where the boom were generated was at a distance of 333 m/s x 150 s = 49.95 Km from the spot where the video was shot. The reason for ...

2

Meteorites and other objects falling through earths atmosphere don't heat up to the temperatures that they do from air friction, but from the compression of the air in front of them. As the frictional heating increased from velocity increase, so would the heat transfer into the surrounding, cool air unless the speed was fast enough, and the object created ...

2

Most meteor showers are associated with comets, they are either remnants of a dead comet or simply orbiting in the same orbit as the associated comet, so their strength can be predicted by how closely earth intersects with the orbit, where the observer is on Earth, and at what point the biggest "clump" of cometary fragments are in the orbit. To use your ...

2

As an incoming meteoroid approaches the Earth, it encounters atmospheric atoms and molecules, some of which are absorbed and trapped in the meteoroid. The generated heat causes atoms to boil off and collide with those in the atmosphere. This produces ionized particles which surround the meteoroid with a glowing envelope leaving a column of plasma. The ...

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