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Keep in mind that Mars and Venus would both be counted as "earth-like exoplanets" if we spotted them from similar distances.

We haven't seen any chemical signatures that are unique to life in any exoplanet atmospheres so far afaik - but that's not saying much since numerous biological processes mirror geological ones but just go faster, at least in terms of processes that produce enough gases to show up in atmospheric absorption spectra.

In short, we have no evidence that cellular life (let alone anything bigger) exists on other planets - but also no evidence that it doesn't, due to the limited abilities of our best instruments.

> bodies of water

Not proof of life. Just a far better chance that life exists, as we know it.

> vegetation on land

Proof of life. Plants are considered as living things because they fulfill all the characteristics of living things.

Plant life began began colonizing land 500 million years ago, during the Cambrian Period, around the same time as the emergence of the first land animals.

Microscopic organisms (microbes) left signals of their presence in rocks about 3.7 billion years old. Microbes would also be considered life as microbes are social creatures that live in communities shaped by cooperation and competition, and they change their behavior, sometimes for the worse, depending on the company they keep.

Speculations of life perhaps but proof would require observing some form of life, which hasn't happened quite yet

I believe when scientists mention ‘earth type’ the only variable they are referring to is distance from the host star to be able to support life. If life exists or existed…?

Bacteria would constitute life.

Having bodies of water does not.

A 15% to 30% oxygen atmospheric content would be a pretty good indicator of some sort of life.

Hello u/NiallMK, your submission "Are 'earth type' planets proof of life?" has been removed from r/space because:

• Such questions should be asked in the "All space questions" thread stickied at the top of the sub.

Please read the rules in the sidebar and check r/space for duplicate submissions before posting. If you have any questions about this removal please message the r/space moderators. Thank you.

Obviously plants and bacteria would be considered life. But we've never detected plants or bacteria on other planets, or any other life. When you hear about "earth like " planets they're only talking about the planets size and how much energy it receives from its star, because that's all we can know about them.

If we knew there was vegetation, that would be proof of life. Plants are alive.

But we can't see exoplanets in enough detail to detect these things. The closest we can get is detecting the composition of the atmosphere.

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Hello u/DumpTrumpGrump, your submission "How fast is air?" has been removed from r/space because:

• Such questions should be asked in the "All space questions" thread stickied at the top of the sub.

Please read the rules in the sidebar and check r/space for duplicate submissions before posting. If you have any questions about this removal please message the r/space moderators. Thank you.

I need a live view of this and a lot of mushrooms to eat

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The max velocity is a sound velocity at the standart condition ( 1atm, 273 K) by sqrt(2/(gamma -1)) where gamma is àn isobar to isochore heat capacity ratio

Because of the way this post is formatted, it appears as if OP asked a question and simply used a picture that, as we have come to find out, is apparently a linked article. At least on mobile.

Air doesn't really have a true 'speed'. There is a 'transfer-of-air' speed that is dependent on pressure. Generally, the more there is a difference in pressure, the faster nearby air will move.

At the surface of the planet, all the air above you puts a pressure of 14 pounds per square inch on everything. We don't feel that, because we evolved to not feel it. You can't see it because that air presses in on every possible direction.

But air kinda has a speed.

The "speed of air" is probably best described as the "speed of sound". Sound in air, like a balloon's pop or someone's shout, is transmitted at about 770 miles an hour, or about 1100 feet per second. When you smack your hands together, someone that's 1100 feet away will hear it in one second. When a lightning bolt causes a thunder clap, five seconds later (almost a mile of distance), you'll hear it.

That's probably the best way to describe how "fast" air is.

Speed of individual air molecules about 500 m/s, so just a bit faster that speed of sound in air.

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Assuming best case (cracked from the top), air will rush in at the velocity dictated by gravity and the mass of the air column directly above it. It would be extremely forceful; the vial, bottle, cup, etc. may not survive the experience. You can create a similar effect with nearly full beer bottles and a good whack – look for videos about cavitation or the "water hammer" effect. XKCD also addressed a similar question in an old "What If?" article, which you may find enlightening and amusing.

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