Can I run as fast as The Flash?

By Rhys L Griffiths

The Flash has been one of DC Comics most popular heroes since his first appearance in the Golden Age Flash Comic #1 in January 1940. Since then he has battled countless villains with his super speedy skills, taken up numerous identities and now stars in his very own TV Show called ‘The Flash’. But how fast is he?

Promotional image for The CW show 'The Flash'

Promotional image for The CW show ‘The Flash’

The Flash is fast. I mean he’s really fast. The fastest thing that we know of is light and The Flash can outrun it. Light travels at 186,282.397 miles per second which means if you were to travel at that speed then you’d be able to go around the world seven and a half times in one second! Although it would have major consequences on your body, we are not built for speed! The Flash, however, is different as he gains his powers from the Speed Force, an extra-dimensional energy that encompasses the universe. This allows him to run at ridiculously fast speeds without damaging himself or the people around him. Unfortunately us humans are unable to use the Speed Force, as it’s fictitious. If we wanted to travel as fast as The Flash then the acceleration that is applied to our body would have a drastic effect.

Scream if you want to go faster!

The human body can withstand any constant speed, but acceleration can have a great impact on our bodies. If a person were to jump out of an aeroplane they would fall at roughly 10 meters per second squared until they reached terminal velocity. Terminal velocity is the speed where the drag of the object falling equals the acceleration and stops acceleration increasing. Travelling at 10 meters per second squared is the fastest you can travel using only gravity, this is referred to as 1G, as in G-force. The more Gs you experience the more weight of force is being exerted on your body. The terminal velocity of a skydiver with their arms outstretched is 120 mph.

Increasing the Gs

The body needs to maintain 22 millimetres of mercury blood pressure to move blood from your heart to the brain. This multiplies with each G added to your speed. So if you were to travel at 2G it would double to 44 millimetres. We can travel at 5G for 2 minutes before passing out, the human body cannot keep up and our blood cannot be pumped quick enough to our brains. If we wanted to travel at the speed of light we would need to accelerate at a manageable speed which would probably take a few months.

Despite this, higher Gs have been achieved. During NASA’s Mercury-era rockets, the astronauts were experiencing 8G and the later Gemini-era Titan rockets would subject them to 7.25G, but it’s still not the most Gs a human has been subjected to. In the mid-40s, Air Force physician John Stapp decided to research how to improve cockpit designs to make them safer. He developed a rocket-powered sled that ran along a track, like a train, which he named the “Gee Whiz”. John Stapp tested it with himself in the seat and administered 35 Gs to himself and survived. He then went on to develop the “Sonic Wind” in the 1950s which accelerated him to 632 mph in less than 5 seconds, then stopped in just one second, generating 46.2G. This meant that his weight of 169 pounds felt as if it was over 7,700 pounds. Stapp walked away from these experiments unharmed as the large amount of Gs were only applied to his body for a very short amount of time.

Typical test setup on G-Whiz. Note the telemetry antenna on the circular platform on the windbrake, and the camera below it. Courtesy EAFB History Office

John Stapp – Typical test setup on G-Whiz. 
Courtesy EAFB History Office

Running at light speed

Usain Bolt currently holds the record of fastest speed by a human when he reached 28 mph during the 100-meter sprint. Despite this, a new study has revealed that humans could potentially run up to 40mph, based on what holds them back and how fast their muscles can move (read the full study here). Humans are nowhere near close to running at light speed, but hypothetically, if I were able to run at light speed, what would happen to my body?

Well firstly when we run, we use energy. Calories are a measurement of energy in food, so when we use energy we burn calories. The faster we run, the more energy we use, the more calories are burnt. But that would mean for someone the same height and weight as The Flash, they would burn

237,000,000,000,000 Calories

running half the speed of light!

In the early episodes of the television series (when he is running nowhere near the speed of light but still breaking the sound barrier), Barry Allen keeps fainting because his glucose levels continuously plummet. To solve this problem he has to eat a lot of food. Given that an average man needs around 2,500 calories per day, that would mean that if you wanted to run at the speed of light you would have to eat a LOT more food. No one has an appetite that big!

But that isn’t the biggest problem. If we were to run at the speed of light, then the air molecules in our path wouldn’t have time to get out of the way. You would tear apart the atmosphere creating a huge atomic explosion that would destroy both you and everything around you, which wouldn’t be good. Howeve,r the flash can move so fast he is able to vibrate his atoms at such a frequency that the air molecules can pass through his mass. It also means he could run through a wall with the wall remaining intact as it would just pass straight through him.

The Flash

Panel from DC’s ‘The New Frontier’ – Showing how The Flash can vibrate his atoms allowing him to run fast. Credit DC

Another problem when it comes to travelling at light speed is that the more energy you put into moving something, the more mass it gains.  Albert Einstein wrote this as E=MC², which means that Energy is equal to Mass, multiplied by the speed of light, squared. It just makes it harder and harder to accelerate, making that light speed goal impossible to achieve.

How fast can The Flash run?

As I stated at the start of the blog, The Flash can outrun light. He doesn’t do it often but he can do if he pushes himself. The Flash has outrun Superman, he has outrun the gravitational pull from a black hole and he has even outrun death. But this still isn’t the fastest he has travelled.

The Flash - The Human Race by Grant Morrison and Mark Millar

The Flash – The Human Race by Grant Morrison and Mark Millar. Credit DC

In ‘The Flash – The Human Race’ by Grant Morrison and Mark Millar, which features The Cosmic Gamblers, who are two alien entities who live at the end of the universe and are entertained by placing bets with one another. The Cosmic Gamblers like to select beings from worlds and make them race, where the penalty of losing is the destruction of the racer’s planet. The Flash is naturally chosen to represent Earth and beats a number of other super speedsters while racing through the universe. But The Flash challenges The Cosmic Gamblers to a race, from the end of the universe back to Earth. The Gamblers love a wager so of course, they accept as they have the ability to teleport so there is no way the Flash can run faster then instantaneous travel.  However, this is where The Flash runs faster then he has ever ran before and manages to get back to Earth faster then his opponents. This means that The Flash must have been travelling a minimum of:

23,759,449,000,000,000,000,000,000,000,000,000,000,000,000 X the speed of light.

If you wanted to say that number then there is some debate depending on where you live. In America a tredecillion is a number with 42 0’s after it, however a British tredecillion 78 0’s. But I think we can all agree that is one large number.

The Flash moves at a speed that is faster then anything we have ever known. The smallest amount of time known to exist is called a Planck instant. This is the length of time at which no smaller meaningful length can be validly measured. We measure this time by seeing how long it takes a photon (a particle that transmits light) to cross one Planck length, the smallest possible distance. So having The Flash run from the edge of the universe back to Earth faster then one Planck Instant, means he has essentially broken speed and entered what is referred to as ‘trans-time velocity’.

A Panel from The Flash - The Human Race - Credit DC

A Panel from The Flash – The Human Race – Credit DC

So can we run as fast as The Flash?

No. No we can’t.


For more Superhero science check out:

The Physics of Thor’s Hammer
Batman V Superman: Who would win?
Can science make a Spider-man?
Could Ego the Living Planet really exist?


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If you are a primary school in Wales and would like us to visit your school, then click here as you may be able to book the show for a reduced price.


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Posted in Biology, Physics