You have probably heard references made to the “dark side” of the Moon – there’s even a Pink Floyd album with that name. But, in fact, there’s no “dark side” of the moon. Because it is not illuminated by the Earth, it is illuminated by the Sun. All the surface of the moon lit by the Sun as the Moon rotates.
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Category Archives: Physics
Why astronauts float in space
We see images and videos from the International Space Station (ISS) where astronauts floating in the space freely. That’s because they’re in the space, so there is no gravitational force of Earth there, right?
How Earth Could Die – 8 Horrible Ways
Now we’re living on a warm, hospitable planet. As Carl Sagan has said “That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives.” We, humans, are the unquestionable rulers of our little oasis in a hostile universe. But all things must pass. The life on Earth, even the planet itself, won’t last forever. What’s more, the humans may go extinct before our planet (and probably before the life on it) dies out.
Here some possible (and horrible) ways how planet Earth could die.
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How Eratosthenes calculated the Earth’s circumference
In 240 BC, the Greek astronomer, geographer, mathematician, music theorist and librarian Eratosthenes of Cyrene (c. 276 BC – c. 195/194 BC) calculated the circumference of the Earth without leaving Egypt. Here’s how:
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How Earth Moves (Video)
A beautiful video, once again, from Michael Stevens, titled “How Earth Moves”. Michael explains many concepts, including “sub-solar point”, “sidereal day vs solar day”, or “how Earth moves in the space” etc, and he is doing it in a very simplified manner. Enjoy!
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Are we the first?
In 1950, the Italian physicist Enrico Fermi was chatting with his colleagues at the Los Alamos National Laboratory(1). They talked about recent rise in UFO reports, then the conversation shifted to other subjects. But during the lunch, Fermi suddenly asked “Where is everybody?”. He was talking about the extraterrestrial life, especially intelligent life. He made some calculations on the probability of Earth like planets, the beginning of life, the probability of intelligent life and high technology and concluded that we ought to have been visited long ago and many times over.
But, there is no reliable evidence aliens have visited Earth and we have observed no intelligent extraterrestrial life with current technology nor has SETI found any transmissions from other civilizations. The Universe, apart from the Earth, seems “dead”.
So, where is everybody?
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Your Life On Earth (presented by BBC)
A nice interactive webpage by the BBC – The British Broadcasting Corporation: how you and the world have changed since you were born? You’re simply entering your birth date, gender and height; selecting units (metric or imperial/US) and then watching how our planet (and you) has changed in your lifetime.
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No! The Earth Would NOT Look Like This Without Water
No, no no, and again: no! The Earth would NOT look like this without water. Please stop sharing this nonsense.
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A Bowling Ball and Feather Falling in a Vacuum (video)
It’s one of the basic Newton laws: how fast something falls due to gravity is determined by a number known as the “acceleration of gravity”, which is 9.81 m/s2 at the surface of Earth. The acceleration of gravity, shortly “a” means that in one second, any object’s downward velocity will increase by 9.81 m/s because of gravity. The gravity accelerates everything at exactly the same rate.
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