Why haven’t we seen the other side of the moon?

Answer by Award-Winning Scifi Author C Stuart Hardwick

The far side of the moon was first photographed by Luna 3 in 1959. The above is a recent image captured by NASA’s LRO.

If you are asking why we can only see the near side from Earth, that’s because the moon tidally locked. It used to spin faster than it orbits, but just as its gravity causes a tidal bulge in Earth, our gravity causes a bulge in the moon.

Tidal bulges are carried along by the rotation of the body in question, and so create a slight gravitational imbalance. Today, this imbalance is pushing the moon away as a rate of 3.5 cm per year and slowing Earth’s rotation by about a millisecond per century. In the past, that same process slowed the moon’s rotation until it’s rotational and orbital periods became the same.

Now the moon’s stuck with it’s tidal bulge facing us. Any perturbation that would tend to turn the moon with respect to Earth gets cancelled out by the pull of our gravity on the moon’s bulge, and nothing is ever likely to disturb it enough to break free.

Will the moon be closer to Earth one day and will it make ocean tides more severe?

No. The moon is drifting away about 4 centimeters a year. Over time it will drift out to space and Earth will have no moon.

Of course, the sun might become a red giant before that, killing everything, but the answer to your question is no.

As a result the tides will become less severe.

However, as the climate warms and the ocean rises as much as it is now, cities and communities near the sea will become flooded. This has nothing to do with the moon.

What are the similarities of the moon and the earth?

Mysteriously, they are made largely of the same materials which casts doubts on the Giant-impact hypothesis (which predicts the moon should be made of 70% material from Theia, the so-called planet that collided with Earth).

Anyway, they are both rocky. Planets beyond Mars are gas giants with rocky moons, so they have that difference, but the earth and Mars are rocky planets with rocky moons.

What planets are bigger than Earth?

The four gas giants are larger than Earth: Jupiter, Saturn, Uranus and Neptune.

Venus is slightly smaller, but very nearly the same size as Earth. Mercury and Mars are smaller than Earth.

So there are 4 planets larger than Earth in our solar system, and they are the four gas giants.solar_system_3

A space ship traveling toward a star system at 99% the speed of light 100 light years away, at what point will they have to start slowing down?

The U.S.S. Enterprise boldly traveled where no person had gone before and boldly goes where no person will ever go in the future. Interstellar travel just isn’t in the cards for humanity because of the distances and the universal speed limit.

A thoughtful question. No simple answer but we can give you cool information!

Actually, it doesn’t really matter whether the star you are going to is 100 light years away or 1 light year away. These are just incredible, inconceivable distances, and although 99% the speed of light sounds nice, we’re not going to get even a hundredth of 1 percent the speed of light. We just don’t have that technology now or ever, as you’ll see below!

There would be no fuel that could power a spaceship faster and faster toward the goal. At a certain point acceleration would have to stop. You would need to save half of your fuel for slowing down at the other end.

So what you’d have to do is accelerate until half your fuel is burned. Then wait. If that fuel got you half way, then you’d start the retro burn immediately and it would take the same amount of fuel to slow down. If half your fuel took you 1/10 of the way then you’d have to coast for 8/10ths more then the last 1/10 burn the last of your fuel to slow down. To get you going 99% the speed of light would require an almost infinite amount of fuel according to Einstein’s theory of relativity – and then you’d have to slow down too!

It would be a one way trip and you wouldn’t know until you arrived if there was anything out there that could be habitable.

Our closest star, Alpha Centauri, is about 4.4 light years away. That number “4.4” misleads us to think that’s not very far, but it’s further away than you can imagine, and that’s just the closest star. This is a distance of about 5.88 trillion miles away, and there’s another number we can deal with: 5.88 (trillion miles).

The fastest we’ve ever gone was on July 4, 2016, when the Juno spacecraft, assisted by Jupiter’s gravity got up to approximately 165,000 miles per hour (265,000 km/h), breaking all previous space speed records. But even if we could increase that speed 81 times faster than Juno, even if we somehow could come up with the incredible propulsion to both speed up and slow down, that would give us the fantastic speed of 13.3 million mph! Can you even imagine that speed? That happens to be about 2% the speed of light, and it would take us 2,200 years to get to Alpha Centauri without even taking the acceleration or deceleration into account at all. So maybe about 4 or 5 thousand years each way, what to speak of 100 light years like you are asking about would take about 44,000 years each way at 81 times faster than we’ve ever gone before.

Your question was if we could go 99% the speed of light for 100 light years. You did correctly identify that there would be a period of acceleration and an equal period of deceleration at the other end of the trip, but honestly not even a fraction of 1 percent of the speed of light is ever going to be achievable. The weight of the fuel alone would be impossible to move.

We can’t give a number for an answer because we’re never going to get that fast anyway. I did try to put the distances into perspective. We are all living in the world of science fiction and don’t want to accept the numbers. Interstellar travel isn’t in our future.

Meet ‘Steve,’ a Totally New Kind of Aurora

Canadian citizen scientist photographers spotted a fleeting type of aurora not seen before, dubbed “Steve,” and scientists have started working out what’s causing them.

Steve seen with the Milky Way over Childs Lake, Manitoba.

While the northern and southern lights have dazzled watchers of the night sky for millennia, vigilant citizen scientist photographers found another type of aurora over the past few years: a short-lived shimmering purple ribbon of plasma. Their intriguing discovery drew the attention of space scientists, who have just begun to study them.

“Dedicated aurora chasers, especially from Alberta, Canada, were out in the middle of the night, looking north and taking beautiful photos. Then farther south they happened to see a faint narrow purple arc as well,” says Elizabeth MacDonald, a space physicist at NASA Goddard Space Flight Center in Greenbelt, Maryland. There’s different physics behind those purple aurora, she says.

MacDonald led a team who observed the aurora by sending one of the European Space Agency’s Swarm satellites through it. The results suggest they’re a manifestation of accelerated and heated charged particles coming from the sunthat interact with a particular part of the Earth’s magnetic field in the ionosphere. The team published their findings in Science Advances Wednesday.

The citizen scientists weren’t sure about what they’d seen, so they called the strange aurora structure “Steve.” The name caught on, and MacDonald and her team kept it, proposing the backronym Strong Thermal Emission Velocity Enhancement (STEVE). While scientists had known about lower-latitude currents of charged particles for decades, they had no idea that they could produce auroras visible to the eye. But now that people have smartphones and digital cameras more sensitive than what scientists had back then, they can pick out these rare aurora, which last only about an hour.

When will humans land on the sun?

After spending hours and hours on the NASA website researching an answer to your question, I finally have come to a date. Never.

It’s not the surface of the sun you have to worry about, but the corona, which I managed to photograph during the eclipse of 2017 in Missouri. Not the best shot but here it is. The corona is even hotter than the sun. We’re not exactly sure why that is, but you’ve got to get through that before you get to the surface! In this picture, taken with a cheap cannon digital camera with a cheap telephoto lens, the moon is blocking the sun. Slight pink marks at the edge are solar flares that were taking place during the eclipse. The white stuff is called the corona. Essentially, this is the sun’s atmosphere. You’re going to burn up there before you reach the burning surface!