Explainer: Gravity and microgravity | Science Information for College students


Gravity is a elementary drive that’s measured because the attraction between any two objects with mass. It pulls extra strongly between objects with bigger plenty. It additionally weakens the farther aside objects are.

You keep on the floor of the Earth as a result of our planet’s mass is attracting your physique’s mass, holding you to the floor. However generally gravity is so small that it may be laborious to measure — or really feel. “Micro” means one thing small. So, microgravity refers to very small gravity. It exists wherever gravity’s pull is far smaller than we’re used to feeling on Earth’s floor.

Earth’s gravitational pull exists even out in area. It does get weaker for astronauts in orbit, however solely by somewhat bit. Astronauts orbit about 400 to 480 kilometers (250 to 300 miles) above Earth’s floor. At that distance, a 45-kilogram object, which weighs 100 kilos on the bottom, would weigh about 90 kilos.

So why do astronauts expertise weightlessness in area? It’s resulting from how orbits work.

When one thing — such because the Worldwide House Station, or ISS — is in orbit round Earth, gravity is continually pulling it again in the direction of the bottom. But it surely’s additionally transferring so quick across the Earth that its movement matches Earth’s curvature. It’s falling round the Earth. This fixed falling movement creates a way of weightlessness.

Numerous individuals marvel if NASA has a “zero gravity room” for astronauts to coach in. However no. It’s inconceivable to simply “flip off” gravity. The one methods to simulate weightlessness or microgravity is to stability gravity’s pull with one other drive, or to fall! This impact may be created on a airplane. Scientists can research microgravity by flying a particular kind of airplane very excessive, then steering it right into a rigorously deliberate nose-dive. Because the plane speeds steeply downward, anybody inside will really feel weightless — however just for about one minute.

Astronauts inside a KC-135 jet float briefly in mid-air
Right here, astronauts expertise the consequences of weightlessness throughout a flight in a KC-135 jet. NASA

Some analysis on the area station has centered on microgravity’s results on the human physique. As an illustration, astronauts’ our bodies bear many speedy adjustments resulting from weightlessness. Their bones weaken. So do their muscle tissue. These adjustments resemble getting older and ailments on Earth — however in quick ahead. The Tissue Chips in House program tries to imitate these quick adjustments in human cells grown on chips. These chips may then be used to rapidly research the consequences of ailments and medicines to assist individuals on Earth.

Lab-grown cells in area additionally may present a extra correct testbed for medicine and ailments. “We don’t absolutely perceive why, however in microgravity, cell-to-cell communication works in a different way than it does in a cell-culture flask on Earth,” notes Liz Warren. She works in Houston, Texas, on the ISS Nationwide Laboratory. Cells in microgravity, due to this fact, behave extra like they do within the physique, she explains.

Astronauts’ our bodies weaken in area as a result of they actually don’t have to tug their very own weight. On Earth, our bones and muscle tissue develop the energy to maintain our our bodies upright towards the drive of Earth’s gravity. It’s like energy coaching you’re not even conscious of. Not surprisingly, then, even brief journeys into area can weaken astronauts’ muscle tissue and bones. Astronauts on the ISS should do a number of train to remain wholesome.

As we plan journeys to different planets, individuals might want to know what microgravity’s different impacts could also be. As an illustration, weightlessness can have an effect on astronauts’ eyesight. And vegetation develop in a different way in microgravity. That’s essential for understanding how crops will likely be affected throughout long-term area journey.

Past impacts on human well being, some results of microgravity are simply plain cool. Crystals develop extra completely in microgravity. Flames behave in uncommon methods. Water will type a spherical bubble as an alternative of flowing because it does on Earth. Even honeybees and spiders construct their nests and webs in a different way once they expertise gravity decrease than what they’re used to on Earth.

This video illustrates how microgravity impacts flames. On Earth, flames take a teardrop form. In area, they grow to be spherical and sit inside a gasoline jacket. NASA experiments carried out aboard the Worldwide House Station demonstrated the function of soot in altering that spherical form.


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