Gravity assists are crucial for space travel beyond Mars

Microgravity environments reduce muscle mass and bone density

Muscles that assist with balance and resistance to gravity are not subjected to their usual workload on the International Space Station. See the type of exercises that astronauts must complete for roughly two hours daily and learn why these movements are necessary to preserve astronauts' muscles, bones, and cardiovascular health.

In a closed space, acceleration cannot be distinguished from gravity

Just as pressing into a door when in a car makes a turn resembles the feeling of being pushed from the side, Albert Einstein’s equivalence principle states that being in a gravitational field feels the same as when a floor accelerates up against you, as in a rocket.

Gravity Probe B verified that rotating objects drag spacetime

The experiment involved attaching four freely floating gyroscopes to a telescope aimed at a distant star for a year. The observed angular shift of the gyroscopes as a result of Earth's rotation pulling on spacetime was approximately 0.0000012 degrees from the amount predicted by general relativity.

Where you are located in a gravitational field affects how quickly you age

The closer something is to the center of a massive object, the greater the strength of the massive object's gravitational field as a result of space-time being depressed more severely. Time passes more slowly the deeper an object is in this gravitational depression, meaning objects in the universe naturally seek to age more slowly.

According to general relativity, gravity is technically not a force

Forces are traditionally viewed as interactions that cause accelerations, such as the force between two magnets pulling them together or pushing them apart. General relativity reframes acceleration by describing motion along the curves of spacetime as natural, and only deviations from those paths require forces.

Planets' high orbital speeds prevent them from falling into their host star

Although the gravitational force attracts a planet and the star it orbits around, the large speed the planet orbits with, which is acquired during its formation process, causes it to continuously miss the star as it orbits around it. This is analogous to theoretically throwing a baseball horizontally faster and faster until it's fast enough to orbit the Earth while attempting to fall to its surface.

Atmospheric drag is causing the Hubble Space Telescope to drift toward Earth slowly

Without interventions to boost the observatory to a higher orbit, Hubble is expected to fall to Earth's surface in the mid-2030s. In the meantime, the telescope is expected to continue to be productive by shifting its mode of operation to rely on a single gyroscope, down from three.

GPS satellites are programmed to account for their faster passage of time in space

The Global Positioning System relies on signals from satellites to calculate locations on Earth by measuring time and distance. However, their orbits, being farther from Earth's center, cause them to experience less gravitational time dilation. These systems would be off by 11 kilometers per day without relativistic corrections.

While the sun's gravity keeps the planets in orbit, their gravity also pulls on the sun, causing it and everything else in the solar system to orbit around a mutual balance point called the barycenter—the true center of the solar system.

NASA plans to build a lunar-orbiting space station to support future missions to Mars

Planned for a 2027 launch, NASA Gateway is a lunar-orbiting space station meant to support Artemis lunar missions and future Mars travel. This resource includes an interactive 3D model of the proposed station's modules and layout.

Why haven’t humans reached Mars?

Mars remains the most viable interplanetary destination due to its relatively habitable orbit. There are many challenges, however, including the huge distance to Mars, the need for advanced propulsion systems, uncertainty over the impacts of long-duration space travel on astronauts, and the need for safe landing techniques and equipment to handle Martian conditions. Human-manned missions to Mars are not likely to occur until the 2030s at the earliest.

Orbital spaceflight requires reaching 23 times the speed of sound

After the spacecraft accelerates up to at least 17,500 miles per hour, space tourists can travel in elliptical orbits hundreds of miles above Earth for days or weeks at a time. Suborbital flights instead max out at about 2,200 miles per hour and travel only 50 to 70 miles above Earth's surface for a few minutes.

Understanding why suction cups rely on Earth's atmosphere to work

When pressed against a surface, air is squeezed out of a sealed volume, causing the internal pressure to drop below the surrounding atmospheric pressure, and this imbalance creates the "sticking." For this reason, astronauts do not use suction cups or related technologies to stay on spacecraft during spacewalks.

The impact of gravitational force on our bodies surprised early coaster riders and engineers

There is only a certain amount of gravitational force that the body can handle before dealing with consequences like short-term vision loss or unconsciousness. Increased scientific understanding has largely reduced these impacts, with engineers combining periods of intense pressure with periods of relief.

Space probes propelled by lasers may one day visit distant planetary systems

Launched in 2016, Breakthrough Starshot is a project to send gram-sized spacecraft to the nearest stars and their planets at 10% to 20% the speed of light after being accelerated by ground-based laser systems. The project requires orders of magnitude advancements to current technology.

Astrobee is a free-floating robotic system helping with routine tasks on the ISS

Three cube-shaped robots use electric fans to fly through the microgravity environment of the International Space Station. They are equipped with cameras and sensors that allow them to "see" and navigate their surroundings to take inventory, document experiments, and move cargo.

What is space sickness?

Mix motion sickness minus gravity with a host of other variables, and you’ve got a recipe for space adaptation syndrome. It can hit anyone, even astronauts who escaped the issue previously. This article details the history and science behind space sickness.

Guide a ship to dock at the International Space Station

Dozens of ships dock at the ISS yearly, rotating astronaut crews and delivering supplies. This simulation lets you try docking a SpaceX Dragon 2 using the same interface and controls as NASA astronauts.

Simulate the precession of Mercury's perihelion

The location of Mercury's closest point to the sun shifted in the sky at a rate of approximately 0.16 degrees per century, or 0.012 degrees more than what was predicted by Isaac Newton due to the gravity of the other planets. General relativity correctly predicted this shift.

How reusable rocket boosters work

Reusable rockets drastically reduce the costs of space travel, saving agencies and companies millions of dollars by preserving expensive, complex boosters and their engines. The advancement required engineers to develop systems that restarted a booster in mid-flight to slow it down before landing.

Five potential ways to achieve time travel

While the author discounts the possibility of traveling to the past, it lays out five hypothetical modes of catapulting into the future: speed, gravity, suspended animation, wormholes, and light. Each has some scientific basis, but none are realistic for humans. Read the article to learn where they offer promise and where they fall short.

According to the Grand Tack model, Saturn stopped Jupiter's inward migration

The model suggests Jupiter migrated inward early in its formation and cleared debris from the inner orbits of terrestrial planets. Saturn's gravitational pull saved what was left of the inner solar system to form Mercury, Venus, Earth, and Mars.

A global list of every space exploration mission

Learn how and why we explore our solar system and beyond with space exploration missions, and find out how you can get involved.

Voyager science teams still collect valuable space data using four active tools

These instruments track magnetic fields, solar wind particles, radio emissions from the heliopause, and hydrogen levels in the outer heliosphere. Even though each Voyager sends data at just 160 bits per second, NASA receives 6–8 hours of tracking data daily.

How NASA measures marsquakes

Most probes sent to other planets and asteroids focus on surface phenomena, but NASA's InSight Lander is interested in looking deeper. Studying marsquakes as well as the red planet's crust and core, InSight provided four years of insight into how the rocky planets of the inner solar system formed.

How the moon moves, an interactive lesson

How exactly does the moon move, and why does it move that way? In this ridiculously comprehensive interactive explainer, you can conduct experiments to see how the moon rotates and as it moves around the Earth, while learning how gravity works by controlling the path and speed of different objects. Dive into this beautiful, simple explainer to learn the basics on gravity and the moon.

Astronauts have repaired genetic damage in space using CRISPR—a molecular tool that can make precise changes to DNA and is used in single-celled organisms to attack invasive viruses.

Track the location of the Voyager probes, currently between 13 and 15 billion miles away from Earth.

Before humans, the Soviet Union and the United States sent animals—including apes, dogs, and cats—to space during the Space Race.

Explore the known asteroids, comets, and spacecraft involved in asteroid studies within our solar system with 'Eyes on Asteroids,' a 3D visualization from NASA.

Planeterrellas create artificial auroras that mimic the atmospheric displays of light by setting up an electric field between two metal balls in a jar filled with a small amount of air.

Apollo astronauts left items in the moon's 'toss zone,' including golf balls, family photos, and bags of human waste, to make room for lunar rocks.

Shooting stars, or meteors, are fragments of asteroids and comets that burn up as they enter Earth's atmosphere, creating streaks in the sky called meteor showers.

SpaceX's S-1 or 'prospectus' revealed many previously unknown details about the company, including its unprofitability despite doing $18.7B in revenue in 2025, exactly how many voting shares Elon Musk will have in the company (roughly 85%), and more.

After 25 people used virtual reality headsets to practice flying with virtual wings—flapping their arms—their visual cortex responded to the wings almost as if they were real arms, treating them as body parts.

Take a 3D tour of the Hajj, Islam's annual pilgrimage to Mecca, undertaken by over 1.5 million Muslims.

Explore chaos in this simulation of two double pendulums, where small differences in the release angles produce wildly different outcomes.

How fusion—which releases energy when two lighter atoms combine to form a heavier atom—differs from fission

Objects can be 3D printed with light by projecting 2D computerized tomography (CT) scans onto rotating cylinders of resin, which solidify upon exposure.

The deadliest aspect of volcanic eruptions is often not lava, but pyroclastic flows—avalanches of ash, gas, and rock that can move more than half the speed of sound.

Power lines are dotted with large, brightly colored balls to improve the visibility of these thin wires to helicopters and small planes and help prevent potential crashes.

Iran's Revolutionary Guard Corps is independent of Iran's regular army and is one of the most powerful and influential military-political organizations in the Middle East.

Studies suggest when you sleep is as important as how much you get, and syncing with your circadian rhythms may lead to less fatigue and improved long-term health outcomes

Telehealth demand for GLP-1s for weight loss is booming as consumers seek easier access.

The price of gas is a composite made up of several different factors, with the federal gas tax making up less than 20% of what drivers pay at the pump.

Use this tool to calculate the dollar value of your parental mental load, from meal planning to coordinating after-school care, then see resources that help generate solutions.

Gerrymandering works through two techniques: cracking opposing voters across districts to dilute their power, and packing them into a few to waste their votes in lopsided majorities.

The word 'jazz' evolved from 'jasm,' 19th-century American slang for 'energy'

Long before Major League Baseball began allowing instant replay for balls and strikes, an umpire reluctantly used the technology to determine whether a hit was a home run, a move that inadvertently ushered in a new era for the sport.

Apeirophobia is an overwhelming fear of living forever, perhaps stemming from the brain's inability to conceptualize an infinite life.