I've studied more than 5,000 near death experiences. My research has convinced me without a doubt that there's life after death.

• Jeffrey Long is a radiation oncologist in Kentucky.
• He's also founder of the Near-Death Experience Research Foundation.
• He says studying near-death experiences has made him a better cancer doctor. 

This as-told-to essay is based on a conversation with Jeffrey Long. It has been edited for length and clarity.

Thirty-seven years ago I was an oncologist resident, learning about how best to treat cancer using radiation. These were the pre-internet days, so I did my research in the library. One day I was flipping through a large volume of the Journal of American Medical Association when I came across an article describing near-death experiences. 

It stopped me in my tracks. All my medical training told me you were either alive or dead. There was no in-between. But suddenly, I was reading from a cardiologist describing patients who had died, then come back to life, reporting very distinct, almost unbelievable experiences. 

From that moment, I was fascinated with near-death experiences or NDEs. I define a near-death experience as someone who is either comatose or clinically dead, without a heartbeat, having a lucid experience where they see, hear, feel emotions, and interact with other beings. Learning more about these experiences has fundamentally changed my view of the universe.

Near-death experiences have common threads

When I finished my residency, I started the Near-Death Experience Research Foundation. I started collecting stories from people who had NDEs and evaluating them with the mind of a scientist and doctor. I make opinions based on evidence and came into this as a skeptic. But in the face of overwhelming evidence, I've come to believe there's certainly an afterlife. 

No two NDEs are the same. But as I studied thousands of them, I saw a consistent pattern of events, emerging in a predictable order. About 45% of people who have an NDE report an out-of-body experience. When this happens, their consciousness separates from their physical body, usually hovering above the body. The person can see and hear what's happening around them, which usually includes frantic attempts to revive them. One woman even reported a doctor throwing a tool on the floor when he picked up the wrong one—something the doctor later confirmed. 

After the out-of-body experience, people say they're transported into another realm. Many pass through a tunnel and experience a bright light. Then they're greeted by deceased loved ones, including pets, who are in the prime of their lives. Most people report an overwhelming sense of love and peace. They feel like this other realm is their real home. 

I haven't found any scientific explanation for these experiences

These experiences may sound cliche: the bright light, the tunnel, the loved ones. But over twenty-five years of studying NDEs, I've come to believe that these descriptions have become cultural tropes because they're true. I even worked with a group of children under five who had NDEs. They reported the same experiences that adults did—and at that age, you're unlikely to have heard about bright lights or tunnels after you die. 

Other people report seemingly unbelievable events, which we can later confirm. One woman lost consciousness while riding her horse on a trail. Her body stayed on the trail while her consciousness traveled with her horse as he galloped back to the barn. Later, she was able to describe exactly what happened at the barn because she had seen it despite her body not being there. Others, who hadn't spoken to her, confirmed her account. 

I'm a medical doctor. I've read brain research and considered every possible explanation for NDEs. The bottom line is that none of them hold water. There isn't even a remotely plausible physical explanation for this phenomenon. 

I've also studied fear-death experiences, like near-miss car accidents

I take a particular definition for NDEs. The person must be unconscious. But there's another type of phenomenon that fascinates me too: what I call fear-death experiences. 

These are situations where you feel your life is in imminent danger. It might be a near-miss car accident or a sudden fall. These people generally don't experience the tunnel and light, but they often report their life "flashing before their eyes."

While some people with NDEs report these life reviews, they're more common with fear-death experiences. People even recall events from toddlerhood that they can't consciously remember but that we can later confirm by talking with family members and others. 

Studying NDEs has made me a better cancer doctor

While I'm passionate about NDEs, my day job still revolves around helping patients fight cancer. I don't tell my patients about my NDE research. And yet, my work with NDEs has made me a more compassionate and loving doctor. 

I'm able to help my patients face life-threatening diseases with increased courage and passion. My goal is to help them have more healthy days here on Earth. But I firmly believe that if and when they pass, they will be at peace.