Category Space

It’s not the fall that kills you, it’s the sudden stop at the bottom.

Bouncing doesn’t come into it. The question is, how fast are you going when you hit something. The faster you are going, the more energy you contain when you hit the ground—energy that now tries to break bones and crush organs like tomatoes on the windscreen of a passing car.

On Earth, the general rule of thumb is that you risk serious injury from any fall higher than you are. On the moon that would have to be adjusted; lunar gravity is only 1/6th as strong, but there is no air—so you will never reach a “terminal velocity” beyond which you don’t speed up any further.

If an astronaut fell 300 feet on the moon, that’s a 91.44 meter drop at 1.633 meters per second per second acceleration (we’ll do this in metric because metric isn’t a stupid, byzantine measuring system). With no air resistance at all, our hapless astronaut will hit the ground after 10.6 seconds, at a velocity of 17.2 meters per second.

How dangerous is that? Well on Earth, to hit the ground at 17.2 meters per second (ignoring air resistance), you’d have to fall from a height of 15.2 meters, or 49.8 feet, or the roof of a five story building. Onto rock or dry sand. Does that sound like a good idea?

No. Such a drop would likely break the spacesuit and would certainly break the occupant.

 

Credit : Quora

Picture Credit : Google

It isn’t true that travel can only occur every two years, but the conditions are far more optimal at those times, essentially making other times unconsidered.

There are different types of Earth-Mars mission trajectories. They don’t all start when Mars and Earth are close. There are multiple factors involved, including whether or not the spacecraft is to come home, whether a gravity assist from Venus is available, and the capabilities of the launch vehicle. However, for the typical one-way mission to get a probe or rover to Mars, we do indeed launch when Mars and Earth are fairly close.

Mars and Earth are at their closest to each other when they are at opposition. However, we don’t actually want to launch at this point. We want to launch before this point.

We want to use a minimum energy transfer orbit in order to use the least amount of fuel. A Hohmann transfer orbit does this. Our spacecraft starts at Earth’s orbit. A Hohmann transfer orbit uses a burn at the starting point (periapsis) that increases the aphelion of the orbit such that it occurs at the orbit of Mars. This will be 180-degrees later in the orbit.

So, our goal is to time the launch such that Mars will be at that same location when the spacecraft gets there. Since Mars is in a larger orbit, it takes longer to move the same angular distance as the Earth. That means we need Mars to be ahead of Earth when we launch our spacecraft.

We calculate the period of the orbit that our spacecraft will be in. That turns out to be about 520 days. Our spacecraft is traveling half of an orbit, so our trip will be about 260 days. Mars has an orbital period of 687 days. In 260 days, Mars will travel an angular distance of 136 degrees. That means the optimal time to launch the spacecraft is when Mars is 44 degrees (180-136) ahead of Earth in its orbit, as shown below. That means we launch the spacecraft about three months before Mars and Earth are at their closest.

 

Picture Credit : Google

On Earth, gravity pulls down on us. In the standing position, that means our head is pressing on our neck, our neck is pressing on our torso, our torso is pressing on our legs, and our legs are pressing on our feet. We lie down, partly, because in doing so we spread the load across our body, taking a lot of stress off of the lower parts of our body.

We also lie down because it leaves us in a stable position, so we don’t have to worry about losing our balance and falling, once we are asleep and no longer actively maintaining our balance.

In an orbiting spacecraft, we are in free fall, so we experience weightlessness. All of those red arrows (loads from gravity) disappear. The body now experiences no change in loading from the vertical to the horizontal position. Both are equally stable and both feel the same.

So, sleeping is done in whatever position best fits the available room.

 

Credit : Quora

Picture Credit : Google

Freeman Dyson may be gone, but his famous alien-hunting idea will likely persist far into the future.

Dyson, a quantum physicist who died at age 96 on Feb. 28, recalled in a 2003 interview just how he first advanced his concept of a “Dyson sphere,” which could betray the existence of an advanced alien civilization. 

A Dyson sphere is a theoretical mega-engineering project that encircles a star with platforms orbiting in tight formation. It is the ultimate solution for living space and energy production, providing its creators ample surface area for habitation and the ability to capture every bit of solar radiation emanating from their central star

Because of their infrared radiation, Dyson spheres are considered a type of technosignature — a sign of activity that distant astronomers could use to infer the existence of intelligent beings in the universe, according to a NASA report. A handful of Earth-based researchers have scanned infrared maps of the night sky in hopes of spotting Dyson spheres, but so far, nobody has seen anything out of the ordinary.

In 2015, astronomer Tabetha Boyajian, then at Yale University, reported on the mysterious dimming of light from a star called KIC 8462852, whose irregular flickering looked like nothing researchers had ever seen before. Other scholars suggested the weird light dips could result from a partially built Dyson sphere, and the idea caused a media sensation. Campaigns to look for other signs of technological activity from the entity, which came to be known as Tabby’s star in honor of Boyajian, have turned up empty, and most researchers now think the object’s light patterns have some kind of nonalien explanation.

 

Picture Credit : Google

Your parents would advise you against sharing your location with strangers. But back then, scientists thought it would be a good idea to reach out to aliens by sending out a map to locate our Sun and thereby Earth. What’s this map like? in space, no one can find you using coordinates such as north, south, east or west. That’s why American astronomer Frank Drake came up with the Pulsar Map. And two of these maps are currently aboard Voyager 1 and 2 probes, which are sailing through the interstellar space. The maps are inscribed on the Golden Record that the probes carry. The records contain sounds and images selected to portray the diversity of life and culture on Earth, intended for any intelligent extraterrestrial life for that may find them.

How does it work?

The pulsar maps on the Voyager probes pinpoint the location of the Solar System with respect to 14 pulsars.

Pulsars are the rapidly spinning remains of dying stars – the leftover cores of supernova explosions. They emit narrow beams of light. Each pulsar has its own signature pulse rate, thus easily identifiable, and ideal as reference points on a map.

Frank Drake’s map has each pulsar connected to the Sun by a solid line. The length of the line represents the pulsars approximate relative distance from the Sun. Along those distance markers are inscribed the pulsars’ spin rates in binary code. By decoding the map, extraterrestrial intelligence can calculate the time frame of the spacecraft’s launch and also the position of the Sun.

 

Picture Credit : Google

Earth is not just a solid ball. It’s interior, as much as its exterior, is a subject of great fascination. You must be aware that Earth’s interior has three major layers: the crust, the mantle, and the core. But did you know there is a vast reservoir of water, three times the volume of all the oceans, deep in the Earth’s mantle?

It is hidden inside a blue rock called ringwoodite and lies 700 km underground in an area called the transition zone in the mantle, the layer of hot rock between the crust and core. Ringwoodite is a rare mineral that forms under very high pressure and temperature, such as those present in the mantle’s transition zone.

The reservoir was discovered in 2014 and it threw new light on the origin of Earth’s water. All along, geologists had thought water came from icy comets as they struck the planet during its formation. But the discovery supports an alternative idea that the oceans came from within the interior of early Earth.

The hidden water could also act as a buffer for the oceans on the surface, explaining why they have stayed the same size for millions of years.

 

Picture Credit : Google